Thread rolling die with twisted slug forming and removal surface



Oct. 15, 1968 R. w. ORLOMOSKI THREAD ROLLING DIE WITH TWISTED SLUG FORMING AND REMOVAL SURFACE 3 Sheets-Sheet 1 Filed Sept. 27, 1966 qll I d m W m W a m W a 3 u 9 0 Wm, ob 9 m8 M Q 0Q W w 9m M 2 w w I 1 2 k w IL 11mm I w I I l -I v .T/Mm, 6m 8 a m a R. W. ORLOMOSKI THREAD ROLLING DIE WITH TWISTED SLUG Oct. 15, 1968 FORMING AND REMOVAL SURFACE 3 Sheets-Sheet 2 Filed Sept. 27, 1966 Rages WOflZomosisii, 65 W, m if 4 r flfiomneys Oct. 15, 1968 R. w. ORLOMOSKI THREAD ROLLING DIE WITH TWISTED SLUG FORMING AND REMOVAL SURFACE 3 Sheets-Shet 5 Filed Sepf. 27. 1966 Rage? United States Patent THREAD ROLLING DIE WITH TWISTED SLUG I FORMING AND REMOVAL'SURFACE. Roger W. Orlomoski, Paxton, Mass., assignor to Reed Rolled Thread Die C0., Holden, Mass., a corporation of Massachusetts Filed Sept. 27, 1966, Ser. No. 582,343-

' 6 Claims. (Cl. 72-469.)

This invention relates to thread rolling dies and is particularly concerned with that type of thread rolling die which produces gimlet pointed screws. .T.

Production of screws by rolling the threads therein through the use of apair of properly grooved dies which are moved past each other with a cylindrical blank squeezed and rotated therebetween is an old and well known art which does not need to be explained to those who are skilled in this field.

However, the production of so-called gimlet pointed screws has presented certain problems posed by the creation of the pointed portion of the screw, which must have thereon a thread which is a continuation of the main body thread and is in the form of a decreasing spiral running to the point. If the blank from which the screw is formed has been initially pointed prior to rolling the threads therein, the problem is somewhat simplified; but this solution calls for a more expensive blank. In such case, the blank must be not only pointed but also exactly the right length. On the other hand, if the blank has not first been pointed, then'as the threaded point is generated during the rolling of the blank between the dies, means must be provided for removing the surplus material that will be present at the lower end of the blank below the threaded point. This surplus portion is known in the trade as a slug.

Accordingly, the problem of designing a suitable configuration for the dies which are capable of rolling on an unpointed blank a perfect screw thread throughout the length'of the body portion as well as on a correctly formed tapered gimlet point while at the same time effectively removing the surplus material below the point has been difficult of solution.

The present invention discloses a new and novel structure with respect to that portion of the die which causes the gradual reduction in diameter and simultaneous pointing of the blank and removal of the surplus therebelow. As the threaded point is formed, the dies simultaneously create the slug therebelow whichseparates from the screw prior to completion of the threading operation. The configuration of the die surfaces disclosed herein that produces this result is unique in that the'instantaneous angle of engagement with the developing slug and the axis of the screw is constantly changing from a maximum angle at the commencement of the point threading operation to a zero angle at the end and the width of the surface in engagement with the blank first increases and then decreases until the slug breaks away prior to the completion of the pointing operation.

The changing anglev and width of the slug creating surface results in effective production of the slug and separation thereof from the body of the screw in a manner that leaves sufficient metal behind to give a full bodied threaded gimlet point.

Gimlet pointed screws as currently manufactured are made with an included angle at the point of approximately 40. That is, the angle of each side of the point with the axis of the screw is approximat'ey 20. The angle of the slug producing surface of the die below the pointing surface with the axis of the screw at the commencement of the pointing-operation is preferably about 20. In the present invention, the angle decreases continuously to about before the slug separates from the bottom of the still uncompleted screw point. The decrease in the Patented Oct. 15, 1968 angularity of the slug producing surface is preferably, but not necessarily, at a uniform rate.

Thus during the early stages of the extrusion of the slug portion away from the screw body the included angle between the sloping grooved surface that produces the point and the slug forming surface shifts progressively from an included angle of to an included angleof at the approximate time of the slug separation. Putting it another way, the angle between the slug producing surface and the axis of the screw decreases from 20 to 0 with slug separation occurring in the vicinity of 5. The slug producing surface in the preferred form might be described as a helical surface if the rate of twist is uniform. However, it is not intended to limit the rate or degree of twist to the helical form, and hence this surface is hereinafter referred to broadly as a twisted surface.

When the blank is at its maximum diameter at the start of the pointing operation, the included angle is at a minimum to provide a maximum pointing and extruding effect. Then as the stock becomes reduced in cross section as the threading operation proceeds, the included angle between the sloping grooved pointing surface and the twisted slug forming surface increases until slug separation occurs. The net result of this is that there will always be sufficient stock remaining between the two sloping grooved pointing surfaces of the cooperating dies after slug separation to produce a full and complete threaded point that will be commercially acceptable.

Throughout this specification and claims the construction of the dies will be described on the assumption that the axis of the blank is vertical and the main grooved thread forming faces of the dies are also vertical. However, the claims are intended to cover all constructions regardless of the particular orientation in space so long as the dies and blank are in themselves in the described relationship.

These and other objects of the invention will become more apparent as the description proceeds with the aid of the accompanying drawings in which:

FIG. 1 is a vertical elevation of one of the pair of identical dies.

FIG. 2 is a top plan View of FIG. 1;

FIG. 3 is an end elevation to double scale of FIGS. 1 and 2 looking from the left;

FIGS. 4, 5, 6, 7 and 8 are a succession of vertical sectional views taken through a pair of dies showing the progressive character of the threading and pointing operation and the production and separation of the slug from the point. For purposes of illustration the thread producing grooves present in the dies both on the vertical surfaces and on the sloping pointing surfaces have been omitted for clarity. Such grooves and the threads produced thereby constitute no part of the invention, as such structures are old and well known;

FIG. 9 is a more detailed representation in a single figure of the changing configuration of the twisted slug forming surface and its effect on the development of the screw point and the progressively extruded slug portion; and

FIG. 10 shows a finished gimlet pointed screw of the type produced by the dies of this invention.

Referring first to FIGS. 1, 2 and 3, the general structure of the dies will be readily recognized. It is to be understood that the operative portions of the two dies are identical. In practice, the moving die is made somewhat longer than the stationary die for the purpose of facilitating entry of the blank to initial rolling position between the dies. The thread forming grooves on both the vertical and sloping pointing surfaces and the slug forming and removal surfaces are identical in the two dies. Accordingly, it will be understood that a description of the single die shown herein is a description of both dies of a pair of dies.

In the vertical elevation shown in FIG. 1, the die 2 has a vertical plane surface generally referred to as A. This surface contains a plurality of conventional parallel V-shaped grooves 4 cut to an angularity and depth capable of producing the required thread when the blank is rolled between the dies in the usual manner.

The lower edge of the vertical grooved surface A forminates in a heel line 6. This heel line is the line of intersection between the grooved surface A and a sloping grooved pointing surface B. The grooves 4 run continuously' across vertical surface A and then into sloping surface B, maintaining the correct depth to produce the required threadon the screw body and point. The surface B terminates in part at a lower edge 8 which is parallel to heel line 6. Another edge 10 runs from the heel line 6of grooved'surface A downwardly and away from surface A at a small angle to the point 12 where it meets and intersects the edge 8. Edge 10 may be referred to hereinafter as the diagonal edge, while edge 8 running from the point 12 to the point 14 may be referred to as the parallel edge. The sloping grooved plane surface B is thus bounded by heel line 6, diagonal edge 10, parallel edge 8 and at the right end by sloping edge 16. All of these boundaries lie in the plane of surface B.

The portion of the die immediately below edge 8 is in the form of a vertical plane surface C. The surface C may be referred to as the flat bumper surface which functions to limit the positioning of the dies toward each other when they are set up in the thread rolling machine. The bumper surface thus acts as an effective means to protect the thread forming and pointing surfaces from inadvertent damage. This bumper surface terminates in part at its left edge at the line 18 and in part at the curved edge 20 which is a portion of the upper edge of a cut-away space indicated at E. The vertical back wall of space E is numbered 22 and the upwardly sloping wall 24.

It will now be noted that between the short left edge 26 of surface A, which commences at the left of the die, the diagonally sloping edge 10, the vertical edge 18 and the upper edge 20 of the wall 24, there is a surface F which extends from the lefthand edge of the die at 28 to the edge 18 at the left of vertical surface C. It is this surface F which comprises the principal novel feature of the invention. This surface slopes in a reverse direction from that of sloping grooved surface B. The angle of the slope at edge 28 may, in apreferred construction, be approximately 22 /2 As the surface F progresses to the right to meet the edge 18 the slope of surface F progressively increases until it becomes vertical at its right end to merge into the vertical edge 18.

The cross-hatching that has been applied to surface F in FIG. 1 has been included to aid in an explanation of the twisted surface. At the left, starting at edge 28, the cross-hatching is at an angle of 22 /2. The hatching becomes progressively more vertical to indicate that the surface F becomes more vertical as it moves to the right. In other words, it may be explained that the surface F is in the nature of a fiat surface which has been twisted. All crosswise extending lines in the surface F, such as those indicated at 30, 32, 34 and 36 in FIG. 1 are approximately straight lines, but their angularity with the vertical decreases from left to right. Thus at line 30 the surface is at 20 to the vertical, at line 32 at at line 34 at 10, at line 36 at 5 and finally at the line of intersection with the vertical extrusion surface C at 18 the twisted surface is at 0.

While the rate of change in angularity is preferably at a constant rate, still the rate may be varied somewhat and might for part of the length of surface F even remain unchanged so long as in the overall the angularity with the vertical does decrease during the production of the slug.

Appearing in FIGS. 1, 3 and 9 is a contour line 38 residing in the surface F. This line lies in the same plane as the surface A. The twisted surface between contour line 38, upper edge of the cut-away clearance space E to 4 the right of point42, the edge 18 and the diagonal edge 10 constitutes a sub-surface G of the larger twisted surface F. The sub-surface G represents that part 'of the twisted surface F which engages the stock as it rolls across and between the dies. This sub-surface G and'that part of grooved pointing surface B both of which meet at diagonal edge 10 act asa downwardly'moving deepening wedge to cause the formation of the gimlet point of the screw and extrusion of that part of the blank that is 'below edge 10. This lower part of the blank is the 'slug that finally breaks away from the partially formed point of the screw.

From the preceding explanation, it will be appreciated that the sub-surface G on the under side of edge 10 and the grooved surface B on the upper side of edge 10 form in effect a wedge of initially very small dimensions just to the right of line 30. This wedge gradually increasesin size as it'progressively moves downwardly and toward the center of the stock-in accord with diagonal edge10. Thus the two cooperating diesgradually form the thread- -ed point and at the same time reduce the'cross section of the blank below the point to cause the slug thus formed to break off in the vicinity of line 36.

The angularity of plane grooved surface B with respect to the blank axis remains constant but the-angularity of the subsurface G to the blank axis constantly changes from a maximum at the starting position 40 to vertical by the time edge 18 is reached. The contour line 38 terminates at the position 42 from which point the upper edge 20 of the cut-away space E then runs gradually upwardly toward but not reaching edge 10. As the diagonal edges of the two dies come closer, the surface G narrows toward the right sufficiently to insure that the slug will break away before the screw threaded point is completely finished. The point is finished by the time the blank has reached position 12.

From the description thus far, it will be seen that the twisted sub-surface G that engages the blank below diagonal edge 10 progressively widens until the contour line ends at 42. Then the surface G narrows as diagonal edge 10 enters more deeply into the blank to free the slug. Thereafter surface G widens to facilitate the finishing of the :crew point and removal of any metal below the pom Reference is now made to FIGS. 4 to 8 which show on an enlarged scale the manner in which the two dies act on the cylindrical blank in producing the main screw threaded body portion and the threaded gimlet point. In all of FIGS. 4 to 8, the grooves in the dies that produce the threads have been omitted for simplicity in illustration. Those skilled in this art will recognize that the finished screw shown in FIG. 8 would of course have a conventional thread on the upper body portion as well as a thread on the gimlet point. Such finished screw is shown in FIG. 10.

In FIGS. 4 to 8, both dies are shown and all parts have been numbered or lettered to be in agreement with FIGS. 1, 2 and 3. The changing angularity of the twisted sur face F can readily be seen in these figures. FIG. 4 is illustrative of the blank and dies when positioned at line 30 of FIG. 1. FIG. 5 is illustrative of the situation when the blank has rolled asfar as line 32. FIG. 6 shows the blank at line 34, FIG. 7 at line 36, and FIG. 8 at line 18. The angularity of the face F in FIG. 4 is 20 to the've-rtical; in FIG. 5, 15; in FIG. 6, 10; in FIG. 7, 5; and finally in FIG. 8, 0.

As shown in FIG. 1, that portion of the sub-surface G that is in engagement with the blank below diagonal edge 10 starts at nothing at position 40 and then gradually widens following contour line 38. At some point surface G reaches a maximum width. In the construction shown in FIG. 1 this is approximately where the contour line 38 intersects edge20 at position 42. Thereafter the surface G narrows and becomes more 'vertical as diagonal edge 10 moves toward the blank axis. Finally the cross section of the blank is reduced enough to cause the slug 44 to break away to fall downwardly in the space E.

The series of views in FIG. 9 shows still more clearly the changing configuration of the blank as it progresses through a pair of dies. For simplicity, only the outline of the left die of the pair of dies shown in FIGS. 4 to 8 is illustrated as it engages progressively one side of the blank W. FIG. 9 shows the sloping grooved surface B, the twisted surface F, the contour line 38 and the subsurface G lying between contour line 38 and diagonal sloping edge 10. FIG. 9 also shows how the twisted subsurface G starts from zero width at the point 40 where edge leaves surface A and begins to cut into the blank. Surface G then widens gradually until the contour line 38 meets upper edge of space E at point 42. Thereafter the twisted surface G narrows until at some point slug 44 is caused to break away.

FIG. 9 also illustrates by means of cross-hatching on sub-surface G the gradual twisting of the surface F from the left to the right starting at the line in FIG. 1 where it is 20 to the vertical and progresses gradually to 0 at the line 18.

The more acute wedging configuration prevailing between the surfaces B and G at the start of the pointing operation facilitates the initial displacement of the metal of the blank. Then, as diagonal edge 10 enters more deeply into the blank and the sub-surface G twists more toward the vertical, proper separation of the slug is assured.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

I claim:

1. A pair of dies for producing gimlet pointed screws from a blank by the rolled thread process, each die of said pair being of identical configuration and comprising a vertical plane grooved surface for creating the thread on the body of the screw, a sloping plane surface having therein continuations of said grooves and extending away from said vertical grooved surface for creating the threaded pointed portion of said screw, the line of intersection of said vertical grooved surface and said sloping grooved surface forming a straight heel line, the said sloping grooved surface having a diagonal lower edge commencing at and extending downwardly away from said heel line at a small angle thereto, said sloping grooved surface also having another lower edge commencing at the end of said diagonal lower edge and being parallel to said heel line, said diagonal lower edge of said sloping grooved 2. A pair of dies as in claim 1, in which in each said die the angle of said sloping grooved surface to said vertical grooved surface is approximately 20 and the included angle between said sloping grooved surface and said twisted slug forming surface varies from about to 3. A pair of dies as in claim 1, in which in each said die said twisted slug forming surface terminates at and merges into a vertical surface that is parallel to said vertical grooved surface and extends downwardly from said other lower parallel edge.

4. .A pair of dies as in claim 1, in which in each said die the width of said twisted slug forming surface that engages said blank increases as the width of said sloping grooved surface increases along part of the length of said diagonal lower edge, said twisted slug forming surface thereafter decreasing in width with the lower edge of said twisted surface approaching but not reaching said diagonal edge, said twisted surface finally merging into a vertical surface that is parallel to said vertical grooved surface and intersects said sloping grooved surface beyond the said diagonal edge.

5. A pair of dies as in claim 1, in which in each said die the included angle between said slug forming surface and said sloping grooved surface increases at a substantially constant rate.

6. A pair of dies as in claim 1, in which in each said die the width of said slug forming surface at the time of separation of the slug produced thereby is less than the maximum width of said slug forming surface acting on said blank prior thereto.

References Cited UNITED STATES PATENTS 3,176,491 4/1965 Mau et al 72469 X 3,196,654 7/1965 Gordon 7288 3,217,530 11/1965 Sato 72-469 MILTON S. MEHR, Primary Examiner. 

1. A PAIR OF DIES FOR PRODUCING GIMLET POINTED SCREWS FROM A BLANK BY THE ROLLED THREAD PROCESS, EACH DIE OF SAID PAIR BEING OD IDENTICAL CONFIGURATION AND COMPRISING A VERTICAL PLANE GROOVED SURFACE FOR CREATING THE THREAD ON THE BODY OF THE SCREW, A SLOPING PLANE SURFACE HAVING THEREIN CONTINUATIONS OF SAID GROOVES AND EXTENDING AWAY FROM SAID VERTICAL GROOVED SURFACE FOR CREATING THE THREADED POINTED PORTION OF SAID SCREW, THE LINE OF INTERSECTION OF SAID VERTICAL GROOVED SURFACE AND SAID SLOPING GROOVED SURFACE FORMING A STRAIGHT HEEL LINE, THE SAID SLOPING GROOVED SURFACE HAVING A DIAGONAL LOWER EDGE COMMENCING AT AND EXTENDING DOWNWARDLY AWAY FROM SAID HEEL LINE AT A SMALL ANGLE THERETO, SAID SLOPING GROOVED SURFACE ALSO HAVING ANOTHER LOWER EDGE COMMENCING AT THE END 